I just noticed yesterday. I was searching for a community, found it and read through a specific post and the comments.

I then noticed that I searched with lemmy.world, no biggie I thought, I switched over to my instance feddit.de and searched for the community, found the same post and didn't see any of the comments or anything like that.

I don't know much about the fediverse but I thought I could access everything from every instance and it didn't matter where I had my account. I'm using the app liftoff for Lemmy.